Amp Deal of the Century!

adam2434

Think I'm gonna snag one too. It looks like a nice little gadget for a portable system to take on vacations.

Jockos

Just got mine and pulled the board out. There is alittle hum with nothing connected. Sounds pretty good. Great little portable amp for $15!

Thanks
Jockos

madmax

I've been here at work all evening listening to these bookshelves and I just don't believe what they sound like!

http://www.radioshack.com/sm-homeplug-digital-receiver-speaker--pi-2104193.html

They have a cheapy 5" woofer and a cheapy soft dome tweeter but they just sound so darn good. I could listen for hours. They reproduce an acoustic bass really nice and the treble is very sweet. I've been listening to BR5-4-9 (modern bluegrass) and Michael Bloomfield (blues) and cannot get over the pleasantness and pureness of the sound. I think a lot of it has to do with the crossover. It is a simple cap crossed over at 10K with the woofer running full range. These are keepers for sure!
madmax

Polk65

A suggestion that you check your amp(s) carefully. Quality control could be better.

Proper use of the black wiring sleeve.


This assembler forgot about the sleeve. The top of the wire doesn't look as bad as what I discovered underneath!


Adjustment.

adam2434

I picked one up yesterday but have not had time to do the mod or power it up yet.

I did notice that the balance knob has a center position, but didn't see/feel one with the bass and treble knobs. Anyone figure out a "0" position for those yet?

ledhed

I think mine ended up sounding worse! There are severe EMI problems, just turning on my CDP causes an audible "pop" I'm going to remove the preamp board and see if it gets better.

madmax

No detent for the bass or treble. That probably saved two cents per thousand manufactured...
madmax

cmy330go

What is the best way to defeat or bypass the tone controls?

madmax

There are various levels of defeating the tone controls.
1. Use resistors to set the same resistance as the POT values when centered
2. Bypass the whole tone circuit
3. Bypass the whole preamp board.

I haven't got deep enough in it yet to give any specifics.
madmax

cmy330go

madmax wrote: »

....I haven't got deep enough in it yet to give any specifics.
madmax

But you'll let us know when you have...right?;)

madmax

Oh yea, when I get time to play.
madmax

fredv

Try this:
1. Pull all the knobs out.
2. Open the case.
3. Unscrew the hex nuts of the control pots (use 10mm socket).
4. Disconnect the cables and wiggle slight to take the preamp board out.
5. Solder the input pin to the wiper to bypass the tone circuit.
6. Put the thing back in reverse directions.

madmax

That would do most of the job. The tone components would still be in place but wired around them. Probably just as good as removing them.


Hey, I found this thread. I figured we couldn't be the only people looking at this thing.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=84685

madmax

fredv

Polk65 wrote: »

Thanks Fred. I was hoping someone with a t-amp would chime in. Can you give any other comparisons between them such as tone and power?

Sorry, Steve. Somehow I didn't see this post.
I only tried 2 pairs of speaker - Monitor 5 and home brew 2 way bookshelves.
In low volume (listen within 4 ft), the t-amp (battery operated) and the RS amp are quite comparable in SQ, the t-amp is more natural whereas the RS has a little more emphasis to the high and the bottom ( I supsect it was due to the tonal circuit and "not flat" settings of the bass and treble). However, the t-amp runs out of steam very quickly when cranking up the volume especially with the M5. Even though the RS amp has some coloration, it does sound more open and airy than the t-amp.

fredv

fredv wrote: »

Try this:
5. Solder the input pin to the wiper to bypass the tone circuit.

Oops, this won't work, this is the same as turning the tone to full settings, back to reading the traces on the PCB :-)

EDIT: run a couple jumper wire from the volume control's wipers to CN3's L and R pins, maybe with resistor in between if gain is too much.

adam2434

How easy should it be to pop the top?

I pulling on this thing pretty hard, and it doesn't want to move. Don't want to break the case.

Am I having a "duh" moment?

adam2434

Screws under the rubber feet, maybe?

fredv

Yes, there are 5 screws, one in the center and 4 under the rubber feet.

adam2434

Thanks Fred, figured it out.

Hooked it up to some Infinity SS-2005 (large 3-way bookshelf, about the size of Monitor 5's) I have lying around and my son's portable DVD player.

Sounds OK, good enough for casual listening. Seemed a little harsh in the highs, but that could be the portable DVD player too. Backing off on the treble knob helped.

It was able to drive the speakers to beyond casual listening levels in the large unfinished part of my basement. The heatsink sure got toasty though.

There is a very small amount of hum with it turned up with no source connected, but really no big deal.

adam2434

madmax wrote: »

I've been here at work all evening listening to these bookshelves and I just don't believe what they sound like!

http://www.radioshack.com/sm-homeplug-digital-receiver-speaker--pi-2104193.html

They have a cheapy 5" woofer and a cheapy soft dome tweeter but they just sound so darn good. I could listen for hours. They reproduce an acoustic bass really nice and the treble is very sweet. I've been listening to BR5-4-9 (modern bluegrass) and Michael Bloomfield (blues) and cannot get over the pleasantness and pureness of the sound. I think a lot of it has to do with the crossover. It is a simple cap crossed over at 10K with the woofer running full range. These are keepers for sure!
madmax

These are the self-amplified speakers, right? Do they have a line-level input so you can connect a standard source directly to them?

I looked at the manual and only saw speaker wire and AC connections.

Thanks

madmax

adam2434 wrote: »

These are the self-amplified speakers, right? Do they have a line-level input so you can connect a standard source directly to them?

I looked at the manual and only saw speaker wire and AC connections.

Thanks

To connect a line level input you must remove the screws that hold the amplifier in then hook up wires to the connector going to the amp board. Almost as easy as the stand alone amp but not quite. For now I just have the wire hanging out but I'll drill a hole and mount a jack eventually. Well worth many times the price if you can find a pair. (Same amp and RF receiving board inside with the four knobs sticking out the front of one speaker).

adam2434

madmax wrote: »

To connect a line level input you must remove the screws that hold the amplifier in then hook up wires to the connector going to the amp board. Almost as easy as the stand alone amp but not quite. For now I just have the wire hanging out but I'll drill a hole and mount a jack eventually. Well worth many times the price if you can find a pair. (Same amp and RF receiving board inside with the four knobs sticking out the front of one speaker).

Walked over to a local RS while my car is getting worked on today. They do have a pair - demo with one speaker having a couple scuffs.

Did you have to solder any wires for jacks?

Does the preamp stage still function - volume, balance, tone controls?

I like this as an all-in-one portable system, but am a novice at modding stuff.

Thanks

madmax

adam2434 wrote: »

Did you have to solder any wires for jacks?

Does the preamp stage still function - volume, balance, tone controls?

I like this as an all-in-one portable system, but am a novice at modding stuff.

Thanks

I soldered mine but you wouldn't have to. You could just take a cheap interconnect, cut it in half and wrap the wires together and tape. Very simple stuff. I can talk you through it.
madmax

MillerLiteScott

Just picked up mine. I will put a screwdriver to it later tonight.


5:05 pm just made the mods to the RS amp and I was surprised by how good it sound especially for $15 bucks. I used my iPod as the source, Monitor 5's and the Monster wire that came with my SDA 2B's. Sounded great.

Plus 1 to Madmax. The hardest part of the mods was getting the little rubber feet off.

fredv

Just received the NOS Amperex 6GM8 tubes, they are frame grid and are very similar to the 6DJ8 family, and best of all, only costed me $4 each. Time to figure out how to squeeze in the tube and the filament transformer in the 1.6" x 4" space :-)

adam2434

madmax wrote: »

I soldered mine but you wouldn't have to. You could just take a cheap interconnect, cut it in half and wrap the wires together and tape. Very simple stuff. I can talk you through it.
madmax

Thanks for the offer, Madmax. I'll let you know if I pick 'em up.

Do the controls work with your mod?

Also, did you just run the line level wire out the port or something?

cmy330go

I bought 2 last week and finally cracked one open yesterday. I must admit that I was rather shocked at how good it sounds. So good that I'm going to RS tomorrow morning to get 4 more.:D


BTW: They're not all for me.:rolleyes:

Polk65

Thanks Fred. I believe a t-amp would be a sideways move for me. A gainclone or glass pre may be in my future.

madmax

adam2434 wrote: »

Do the controls work with your mod?

Also, did you just run the line level wire out the port or something?

Yes, all the controls work.

I just left the screws a little loose on the amp and ran the wire out through the crack for testing. At some point I'll order a jack and hook that up.
madmax

madmax

MillerLiteScott

I painted some white reference lines on my control knobs today. Know I know where the volume, balance, bass and treble are without question.

KISS

Sounds good.